It is known that bodies formed by bending sheet-metal blanks into tubular shapes may be welded by laser along their longitudinal seam, particularly with a butt joint, so that welded tubes are formed. These tubes, whose cross-section may be of any desired shape, can be formed, particularly by a subsequent hydroforming process, into shaped bodies that can be used in various fields, and particularly in motor vehicle body construction. JP 02076648 A shows an apparatus with two working zones for coiling and welding strips around an object. Coiling takes place in one zone, and welding in the other. JP 04118191 A shows the welding of various tube sections which are arranged and aligned coaxially one after another for welding. JP 09029477 A shows tube welding with a revolver-like rotatable holder for several tubes. WO-A 98/26898 shows the welding of flat parts that are fixed adjacent to one another on tables, by means of a single laser able to serve both tables.
It is an object of the invention to provide a more efficiently designed apparatus for the manufacture of tubes.
According to the invention, the foregoing object can be realized by apparatus including a table having a holding means arranged for parallel holding of at least two tubes, and a laser beam source whose laser beam emission head, which is arranged above the table, is traversable in the longitudinal direction of the table and is traversable in the transverse direction by traversing one of the emission head and the table. The holding means have clamping jaws that can be shifted into position towards and away from one another. A device is provided for detecting the position of the welding edges of tubes over the length of the tube.
The invention also can include methods practiced in accordance with the teachings herein. In one method for welding the longitudinal seam of tubes by means of a laser beam, a table is provided which has holding means arranged for parallel holding of at least two tubes, and a laser beam source whose laser beam emission, which is arranged above the table, is traversable in the longitudinal direction of the table and is traversable in the transverse direction by traversing of one of the emission head and the table. The holding means have clamping jaws that can be shifted into position towards and away from one another, and a device is provided for detecting the position of the welding edges of tubes over the length of the tube. A tube to be welded is loaded into the parted clamping jaws and positioned in the clamping jaws by at least one of: shifting it forward and back; and rotating it, as directed by the device for detecting the position of the edges, until the correct welding position of the tube is obtained, and in that the clamping jaws are then closed and the tube is welded.